Hello. First of all, it depends what will you do on your computer. Are you a gamer? or just want to use the internet etc ?
Secondly, there are 3 things that link together; 32 or 64bit OS, processor and motherboard. They all need to match to each other. For example different processors need different sockets on the motherboard, and if you want a 64bit OS your processor needs to handle it.
Any hard drive will be good for any motherboard these days, just make sure its an "Internal SATA".
Lastly, when you buy a new hard drive, it DOESN'T come with an OS. You have to buy windows (or download linux) on a CD then install it.
Hope i helped, if you need more info ask